This section provides background information related to the present disclosure which is not necessarily prior art.
A laser light source, which is a solid-state light source, has become an option of an emerging projection light source due to a series of advantages including high luminance, high efficiency, a long lifetime, a good color gamut, greenness, etc.
In an existing light source including laser and fluorescence generated by excited fluorescent powder in the industry, blue laser is typically used as an excited light source of a laser projection system, and also as light in blue which is one of the primary colors including red, green, and blue. A fluorescence wheel is a wavelength conversion device configured to generate light in the other two primary colors than blue light. In an implementation of the prior art, blue laser is emitted onto the fluorescence wheel to excite green fluorescent powder and yellow fluorescent powder so as to generate green light and yellow light respectively, where the green light and the yellow light passes a green light filter sheet and a red light filter sheet of a color filter wheel, thus resulting in green and red light, and blue laser is transmitted directly through the fluorescence wheel, and a transparent region of the color filter wheel without being filtered in color, and enters a light path system, so that the three primary colors including red, green, and blue are output from the color filter wheel as a result.
Moreover some yellow light is typically added to the system for higher brightness, and the yellow right generated by the fluorescence wheel is transmitted directly through the transparent region of the color filter wheel, thus resulting in monochromatic yellow light, so that blue laser passes the fluorescence wheel and the color filter wheel, thus resulting in the monochromatic light in the three respective primary colors, and the monochromatic yellow light. Thus it is necessary to synchronize the fluorescence wheel with the color filter wheel so as to generate the monochromatic light in the three respective primary colors, where only one color is output through the color filter wheel in a timing period, for example, if green light is output by the fluorescence wheel, then the color filter wheel will be rotated accordingly to the green light filter region; otherwise, different colors may be output and mixed with each other, and thus altered, and the proportion of the three primary colors may also be varied, so that the three primary colors can not be timed and output normally.
In the prior art, both of the wheels are synchronized typically in a coaxial design, and as illustrated in FIG. 1, a fluorescent powder wheel 11 and a color filter wheel 12 are connected coaxially, and lie in their respective planes which are parallel to each and placed on an emitted light path of a laser light source 13; and in the dual color wheels, color regions of the fluorescent powder wheel (including fluorescent regions and transmissive region, where the color of the transmissive region can be regarded as the color of laser transmitted through the transmissive region) correspond to three color filter regions distributed on the color filter wheel, and the dual color wheels are rotated in synchronization by driving them into rotation at some frequency using the same motor 14.
In the design above, the boundaries of the same color region in the fluorescence wheel and the color filter wheel need to correspond precisely to each other, that is, projections of the boundaries of that color region in the two wheels onto the axis shall coincide with each other. However this structure may be difficult to assembly in a process, and an offset error occurring in machining and installation will exist all the time because the two color wheels and their wheel axes are fixed. Due to the phenomenon of color mixing due to this error, the purity and the timing at which the colors are output typically have to be guaranteed by removing those mixed components of two colors, which coincide with each other at by some angle, at the cost of lower brightness of the respective monochromatic light.
It is desirable to propose a method for controlling dual color wheels to be synchronized so that the two wheels can be synchronized consistently even if they are not coaxial.